Various lasers and other devices that manage light can be sensitive to temperature, and a light processing outcome or result may depend upon device temperature. For many lasers, lasing wavelength shifts according to temperature of a gain medium and/or an associated feedback element. Often, the wavelength shifts gradually with changing temperature and then abruptly changes in connection with a “mode hop.” Further, lifetime of a laser typically shortens with heightened operating temperature. Running the laser at an elevated temperature increases probability of failure as compared to running the laser in a cooled state.
One conventional approach to addressing temperature sensitivity involves actively cooling the laser with a thermal electric cooler (“TEC”) system that creates a regulated operating temperature. The TEC system keeps the laser cool to avoid shifting of the laser's wavelength and to prolong lifetime.
However, introducing a TEC into a lasing system can pose formidable issues, including disposing heat the TEC has extracted from the laser. TEC cooling involves transporting heat that has been removed from the laser, along a path that may traverse and adversely affect other electrical, optical, or optoelectronic devices. Moreover, handling the extracted heat typically entails deploying other thermal management devices, such as heat sinks, air conditioners, fans, convection systems, etc., that introduce their own set of complications. As another issue, TECs and associated equipment consume substantial amounts of electrical power, thereby involving support power supplies and operating expenses. As another issue, most conventional TECs are typically large, perhaps one hundred, one thousand, or even more times larger than a tiny laser die that is cooled. In many potential applications, space is a premium and compact designs are desirable.
Another significant issue concerns packaging TEC-cooled lasers and other optical devices. When a TEC cools a laser (or other device) below an ambient temperature or a temperature of an operating environment, any water vapor or humidity of the environment tends to condense on the surfaces of the cool laser. This effect is analogous to the common experience of condensation forming on the exterior surfaces of a glass of ice water setting on an outdoor table in a humid summer day. Such condensation can cause significant problems with optical, electrical, semiconductor, and/or optoelectronic devices. Problems can include material degradation, electrical shorts, impedance variations, and interfering with a light beam's propagation via diffracting, scattering, refracting, or otherwise changing the beam. If condensation forms on a surface upon which light is incident (or through which light passes), the condensation can disturb or distort the incident light, analogously to the manner in which condensation formed on a bathroom mirror distorts a reflected image. To avoid formation of condensation, cooled optical communication lasers typically are sealed in hermetic enclosures that prevent permeation of water vapor to optical surfaces, gaps through which light passes, and sensitive components. Any water vapor or other detrimental containment that does enter an enclosure is captured by a special chemical substance (known as a “getter”) placed inside the enclosure. Unfortunately, hermetic enclosures typically pose significant issues related to complexity of manufacturing, baking operations, heightened material expenses, and increased size.
In view of the foregoing discussion of representative deficiencies in the art, need exists for improved technology that can address thermal issues and sensitivities of optical devices, including lasers with outputs that vary according to operating temperature. For example, need exists for a technology that can support achieving tightly controlled optical parameters with non-hermetic packaging, without thermal electric cooling, with power efficiency, with compact size, with long life, with economy, and/or with manufacturability. A technology addressing one or more of such needs, or some other related shortcoming in the art, would promote optical applications including, but not limited to, greater utilization of high-speed optical communications.